Single Point Acquisition
This technique is one of the most commonly used where the operator sets the base station up, turns it on, and via the DJI Pilot App, commences flying as soon as the base station status changes to ‘Connected’.
As detailed in the technical specifications for the base station, the positional accuracy for a single point is as follows:
This means that whilst the relative accuracy will be 1 – 2 cm, there will be large errors for the absolute accuracy. There will be a horizontal error of at least 1.5m horizontally and 3m vertically. This can be a problem should multiple flights need to be carried out of the same area over a period of months/years and you are wanting to compare the flights to each other. For example if you want to compare the ground level in one flight to another, which was carried out on a different day.
Or if you're flying over a large area, involving multiple flights and keep moving the base station, but want the flights to be merged to create one data set.
Manually Entered Coordinate
If known points have been set out and surveyed in using survey grade equipment, then you can enter the coordinate of the known point into the control under the Advanced Settings of the D-RTK 2 base station.
As shown below, go into the Advanced Settings -> Adjust Coordinates.
You can now enter the coordinates of the known point that the base station is setup on. Click OK and you are ready to continue you flight preparation.
For other models of base station, please refer to the manufacturer's instruction manual on how to enter or adjust the coordinates of the base station.
Using an NTRIP provider will provide real time RTK corrections via the internet directly to the controller of the drone, without the need for a base station. This will use a virtual base station relative to WGS 84 and therefore will not only provide high relative accuracy, but also high absolute accuracy.
There can be subscriptions costs associated with this and the operator needs to ensure a stable internet connection to obtain the corrections. If the NTRIP link goes down, then the RTK corrections will be lost.